1. Field of the Invention
This invention relates to a means for driving the back walls of a bucket excavator. More particularly, this invention relates to a means for driving the back wall of a bucket excavator which utilizes a constrained chain which is engaged with two sprockets, and a plurality of push rods which are pivotally attached to the chain and to the back walls.
2. Description of the Prior Art
References made to the following U.S. Pat. Nos. Satterwhite, 3,896,571, "Multi-Wheeled Excavator and Conveying System," issued on July 29, 1975; Satterwhite, 3,897,109, "Multi-Wheeled Excavation and Loading System," issued on July 29, 1975.
The two Satterwhite patents show and describe an excavation system which incorporates several rotatable excavation wheels provided with a plurality of digging buckets disposed between each of the wheels. Each digging bucket is provided with a cutting edge extending slightly beyond the rim of the excavation wheel. The cutting edge extends inward to form a stationary front wall. The backwall of the digging bucket is pivotally mounted on the excavation wheel near the rear surface of the front wall of the next bucket along the circumference of the excavation wheel. The back wall pivots so that it is free, opposite end is adjacent its associated front wall. As the excavation wheel is rotated against the material to be excavated, the cutting edge collects material which is forced inward along the front wall and against the back wall by the later collected material. It is desirable to dump the collected material on to a conveyoer to remove it from the operational site. As the excavation wheel is rotated, each digging bucket, which is now filled, passes adjacent to a conveyor belt. While the digging bucket is adjacent to the conveyor belt, it is desirable to pivot the back wall outwardly becuase the movement of the back wall will result in the dumping of the material from the digging bucket.
The Satterwhite patents described several different means for driving the back wall. One means disclosed is an unconstrained chain with push rods attached at one end to the links of the chain. The push rods are pivotally attached at an opposite end to the back wall. The chain passes over a roller which urges the push rods outward and, in turn, the back wall pivots outwardly along the front walls dumping the excavated material. The chain is unconstrained and is subject to all the streses, instabilities, and breakdowns known in the art to occur with such unconstrained systems. For example, the pivotal connecting links are not rotatably connected to the links of the chain and a torque will be present at the connections between the chain links and the pivotal connecting links. Therefore, the pivotal connecting links will not be aligned but rather will be twisted relative to the direction of movement of the chains. Any jerk which occur will not be evenly distributed down the links of the chain because of the twisting movement.